1. Field of the Invention
The present invention relates to a reflection type semiconductor display device of a direct viewing type, and more particularly, to a reflection type liquid crystal display device (liquid crystal panel). The present invention also relates to a semiconductor device with a reflection type liquid crystal display device mounted thereon.
A semiconductor device as referred to in the present invention may be, for example, information processing equipment such as a notebook-sized personal computer, a lap top type personal computer, an electronic notebook, or a mobile computer, a video camera, a digital still camera, a car navigation system, or a cellular telephone.
2. Description of the Related Art
Recently, an intensive study and development have been carried out with regard to manufacturing technology of liquid crystal panels to make it possible to provide liquid crystal panels at a relatively low cost. Further, as the information society where Internet, electronic mail, and the like are utilized has been developed, notebook-sized personal computers (hereinafter abbreviated as notebook-sized PCs) have rapidly become more popular.
With regard to digital still cameras and video cameras, as they have been allowed to have liquid crystal panels mounted thereon such that images taken can be viewed on the spot, they have become widely accepted by consumers.
Liquid crystal panels fall into transmission type ones and reflection type ones. In a transmission type liquid crystal panel, illumination light is transmitted through the liquid crystal panel from a back light provided at the back so that the user can visually confirm the display. On the other hand, a reflection type liquid crystal panel does not need a back light, and the display can be seen through reflection of external light on the liquid crystal panel. Such a back light consumes about 90% of power consumption of the transmission type liquid crystal panel, and thus, power consumption of a transmission type liquid crystal panel is large. On the other hand, though the display quality level of a reflection type liquid crystal panel is inferior to that of a transmission type liquid crystal panel, power consumption of a reflection type liquid crystal panel is smaller than that of a transmission type liquid crystal panel, and thus, a reflection type liquid crystal panel is advantageous when used in a notebook-sized PC or a mobile PC.
One reason of the inferiority of the display quality level of a reflection type liquid crystal panel to that of a transmission type liquid crystal panel could be the insufficient amount of light when it is used indoors.
These days, in order to solve the problem of the insufficient amount of light, a technique to provide a reflection type liquid crystal panel with a front light is adopted to supplement insufficient amount of light when it is used indoors. However, in this case, since a fluorescent lamp similar to that used as a back light of a transmission type liquid crystal panel is used as the front light, leading to larger power consumption, the advantage of a reflection type liquid crystal panel cannot be obtained.